1. Field of the Invention
This disclosure relates generally to a biorefinery and method for the conversion of carbonaceous feedstock into synthesis gas conversion products. More specifically, this disclosure relates to a biorefinery and method for the conversion of carbonaceous feedstock to liquid hydrocarbons via Fischer-Tropsch. Still more specifically, this disclosure relates to a biorefinery and method for the conversion of carbonaceous material to Fischer-Tropsch products wherein at least one byproduct of Fischer-Tropsch conversion is utilized to produce additional synthesis gas for Fischer-Tropsch synthesis.
2. Background of the Invention
Processes for the production of synthesis gas from carbonaceous materials utilize gasification of a feedstock comprising the carbonaceous materials in a so-called ‘reformer’ to produce a stream comprising synthesis gas (i.e. hydrogen and carbon monoxide; also known as ‘syngas’). The product synthesis gas generally also comprises amounts of carbon dioxide and methane and may also comprise minor amounts of other components. Generation of synthesis gas is disclosed in numerous patents.
Synthesis gas produced via gasification of carbonaceous materials can be converted into other compounds in a so-called Fischer-Tropsch reaction. Fischer-Tropsch (FT) synthesis can be used to catalytically produce synthetic liquid fuels, alcohols or other oxidized compounds. FT synthesis occurs by the metal catalysis of an exothermic reaction of synthesis gas. Fischer-Tropsch (FT) technology can thus be utilized to convert synthesis gas to valuable products. Hydrocarbon liquid products of various Fischer-Tropsch processes are generally refined to produce a range of synthetic fuels, lubricants and waxes. Often, the Fischer-Tropsch process is performed in a slurry bubble column reactor (SBCR). The technology of converting synthesis gas originating from natural gas into valuable primarily liquid hydrocarbon products is referred to as Gas To Liquids (GTL) technology. When coal is the raw material for the syngas, the technology is commonly referred to as Coal-To-Liquids (CTL). Fischer-Tropsch technology is one of several conversion techniques included in the broader GTL/CTL technology. Desirably, the synthesis gas for subsequent production of valuable products via Fischer-Tropsch is produced from ‘green’ materials. For example, an environmentally-friendly system for the production of synthesis gas, which may subsequently be utilized to produce Fischer-Tropsch products, would desirably allow for the production of synthesis gas from carbonaceous materials, such as biomass, which may generally be considered waste materials
The catalyst used in the Fischer-Tropsch reactor and, to some extent, the temperatures and pressures used will determine what products can be obtained. Some Fischer-Tropsch processes are directed to the production of liquid hydrocarbons. Such processes generally utilize iron-, ruthenium, or cobalt-based catalysts. Iron-based catalysts are generally operated with a synthesis gas having a molar ratio of hydrogen to carbon monoxide in the range of from about 0.7 to about 2.0. Cobalt-based catalysts are generally operated with a synthesis gas having a mole ratio of hydrogen to carbon monoxide in the range of from about 1.8 to about 2.2. For example, carbon monoxide and hydrogen can be converted to alkanes over a cobalt-thoria catalyst. U.S. Pat. No. 4,609,679 teaches the use of ruthenium combined with tantalum, niobium, vanadium or mixtures thereof to selectively catalyze for the production of methane. As mentioned hereinabove, other Fischer-Tropsch processes are directed toward the production of alcohols.
Accordingly, there is a need in the art for systems and methods for the production of synthesis gas conversion products from carbonaceous materials. Such systems and methods should preferably enable the environmentally-friendly production of synthesis gas conversion product, for example, by allowing the production of synthesis gas from sustainable and renewable feedstocks such as biomass, facilitating sequestration of carbon dioxide, and/or reducing the amount of waste material produced.